I think you could build a rotisserie to work on your panel, similar to what I did for my cab. You'd need an attaching bracket to the firewall and brackets to bolt to the rear door hinge locations. I used mine with an extension tube between the two engine stands and put my frame on it for painting as well.
I don't know if rotisseries are available to rent, but you'd have to check around your area. The manufactured ones have pretty complicated (adjustable) brackets that use the body mounts. Pretty spendy to purchase.
[on edit] Here's a link to some photos of another member's (older) panel on a rotisserie:
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